MATHS QUESTION!! please help

i have some questions for homework that i just do not get. the question is that i need to make y the subject of the formula can someone please explain how to do these so i know in the future these questions are:

1. 2x+3y=0

2. x+2y=4

3. 1/x+1/(x+y)=0

4. x^2+y^2=1

thanks to anyone who can anwser these

1. 2x+3y=0
3y=-2x
y=-2x/3

2. x+2y=4
2y=4-x
y=(4-x)/2

3. (x+y){1/x+1/(x+y)}=0
(x+y)/x+(x+y)/(x+y)=0
x{(x+y)/x+1}=0
x+y+x=0
y=-2x


4. x^2+y^2=1
y^2=1-x^2
y=(square root 1)-x

Solve for y... For instance in #1.... First put x & y on separate sides of the equation... 3y=-2x and then divide both sides by 3 to get... Y=(2x)/3...

#2 is done the same way 2y=4-x..... Y= (4-x)/2.... Or Y=2-(x/2)....

1. 2x+3y=0
y = -2x/3